Trailer Wiring Issues – What Could The Problem Be?

The wiring in your trailer can cause you some terrible headaches. When the taillights on your trailer don't work as they should, you cannot safely haul the trailer on the roads. If you are having troubles with the lights on your trailer, you may find some relief after using the following troubleshooting techniques.

Determine whether the Problem Is With the Vehicle

Before you go wracking your brain trying to find the problem in the trailer, you have to determine if the problem is, in fact, in the trailer – it is possible that the wiring problem is in the vehicle that you are towing the trailer with.

Use a probe-type 12V circuit tester to test the 4-way plug on the back of the towing vehicle. Get someone to help you during this test to expedite the process. As the signals and brakes are initiated, the tester should display a power reading. If you get no reading during this test, the problem is likely in the vehicle and not the trailer

Follow the wires from the rear of the vehicle to the front examining them closely. If you find any damage in the wires, they will need to be replaced. If the wiring appears to be in good condition, check all of the connections and the fuses. Use the circuit tester to retest the plug on the vehicle. If the test fails, take your vehicle to an electrical mechanic for professional repairs.

Find the Trailer Wiring Problem

If you have ruled out the vehicle as the cause of the problem, it is time to look into the wiring on the trailer itself. Follow the wiring from front to back looking for breaks, kinks or loose connections. If you notice any issues, rectify them and test the lights.

You will notice a white wire in the wiring system – this is the ground wire. This wire must be connected to an area of the trailer that is free of corrosion and debris. If the ground is not connected to the trailer properly, the entire lighting system will not work as it should. The problems a bad ground could cause include:

  • Signal lights activated on both sides when only one is turned on
  • One light doesn't work as it should
  • Trailer lights won't turn on at all
  • Trailer lights turn off when the vehicle's headlights are turned on
  • Trailer lights don't turn off when the signals or brakes are not on

If you have completed the above steps and still have not found the problem with your trailer's lighting, take it in for professional inspection and repairs. Hauling a trailer with malfunctioning lights is not only dangerous for you, it is dangerous for other drivers on the road, so don't put this repair project off.


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